Technology takes the lead in the
Mercedes-Benz SL600, with V-12 turbo engine, adaptive suspension and electro-hydraulic brakes. This is not be confused with the SL55 AMG and SL65 AMG models which are very similar and hafve similar levels of performance. Confusing it is.
Mercedes-Benz poured all its new electronics into the top SL models, and combines that with massive, powerful engines, and the cunning Vario-roof – a steel convertible top. A technological tour de force, and the flagship of the range. Except for the AMG versions (SL55 and SL65 AMGs).
All the SL series are limited to 155 mph, but of course you get there much quicker the bigger engine you have – only 4.7 seconds to 60 mph for the SL 600, against 6.1 seconds for the entry level SL350. Unless you want to make yourself look important with an SL350, you’d do better with the SLK350. It’s more nimble, and gets you to 60 mph in 5.6 seconds, and won’t use as much gas.
There again, you might lust after the technological density of the SL, but you’ll need to get an SL500 or SL600 to get all of those. The point is that although the SL600 is the star, you can get a less powerful model if you prefer.
New looks, setting the new Mercedes image
These are new-look Mercedes models, which set the style which was lengthened and lowered for the SLR McLaren, and scaled down for the SLK. Very distinctive, with those twin headlamps aside of the new-look Mercedes grille which as a massive three-pointed star in the middle. There is a distinct wedge line from the low nose, and it looks just great till you get to the rather washy tail despite the sharp cut-off.
But the new shape works; first, it looks great, and second it looks like the luxurious supercar it is. And thirdly, it’s slippery – the drag coefficient is only 0.29, which is as good as anything around.
So what’s this technology that’s been ladled into the SLs to combat BMW and others? You’ll get:
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Sensotronic braking – this is electro-hydraulic braking, with a pedal reacting to your foot electronically, and telling the hydraulic system how much effort to apply
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Active body control – a sort of semi-active suspension that reduces roll and pitch by about half
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ABS, traction control, stability control and emergency brake assist
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Wishbone front suspesnion and multi-link rear suspension
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Bi-Xenon headlamps, which are twice as powerful as halogen
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Powerful engines and on the SL500, a seven-speed automatic option
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The Vario-roof steel convertible
But what about this power? The SL500 is powered by a moderately tuned 5.0 liter with three valves per cylinder. It develops just 306 bhp at 5,600 rpm, with 340 lb ft torque (460 Nm) at 2,700-4,200 rpm. More like an engine for a sedan, really; just 60 bhp per liter. With a 0-60 time of 6.1 seconds it just about creeps into the supercar class.
Big V-12 in SL600 shoves out 500 bhp
The SL600 is more of a power machine, powered by the magnificent Mercedes-Benz 5.5 liter V-12. It’s from the same family as the V-8, so it has three valves per cylinder, but is a 60-degree unit. For the SL, they developed a twin turbocharger version – this from the company that has been touting the advantages of superchargers for some years.
Well, does it work? Yes, you get 500 bhp at 5,000 rpm (yes, right down there) with masses of torque, almost wherever you prod the gas pedal – 590 lb ft (800 Nm) from 1,800 to 3,600 rpm. Awesome, and a good deal more awesome than the power output, which was presumably limited to 500 bhp.
In any event, the reasons for the turbos is that Mercedes-Benz has found that the twin turbo approach can take up less room, cost less and give almost the same spread of power you get with a supercharger.
Powerful engines in many Mercedes these days
Mercedes-Benz has been chucking its big engines into everything that they could think of lately. This desire to produce really powerful models across the range has given them a bit of a problem deciding how much power to put into each car. For example, there’s a SL65 AMG with 612 bhp from the V-12 which is serious competition for the much more expensive SLR McLaren.
At the other end, you can get the SLK55 AMG which despite only 355 bhp can compete well with the SL500.
So, in the SL600 you get 500 bhp. Sorry, but that’s the way it is. Mind you despite the weight of the SL, that’s a lot of ponies, and boy can they buck at almost any speed on wet roads.
Seven-speed box the star on SL500
The plot gets a but hazy when it comes to transmissions, too. You see, you can get the Mercedes 7G-Tronic on the SL500, which is a seven-speed full automatic, with Tipfunction, as they call their manual control. This gives you and the computer plenty of gears to play with for better acceleration and control.
But once you get up to the massive power and torque – and it’s torque that matters most – of the SL600 there’s just one transmission, the five-speed automatic with Tipfunction. Now, don’t get me wrong, that automatic will transmit the power plenty quick enough, and it is probably OK on this model which is at the luxury rather than sporty end of the supercar market. This is one more way in which the SL600 lacks the bite of a true supercar.
Wishbone front suspension
What about the suspension? Hooray, the guys at Mercedes-Benz have finally admitted that you need wishbone front suspension for the wheel control you want on a sports car – so the SL gets it. At the back, you get a multi-link system, which is basically wishbones with some active control of the toe-in as the suspension moves.
Evidently the suspension is set up for understeer, which is not quite such good news, especially since it has stability control. Nearly all the suspension components are aluminum, and the links are forged for strength.
ABC semi-active suspension
But the SLs don’t get simple coil spring suspension, they get a form of semi-active suspension called Active Body Control (ABC). To limit roll and pitch, there is a small hydraulic ram below each spring. They are computer controlled and the computer receives a lot of information from sensors, , including those used for the stability control and they also measure the weight they are carrying. Yes, all the time.
How does it work? When you start off, the computer decides how much weight is being carried on each wheel, and sets the ride height. If you stop and take your luggage out, it adjusts the ride height. When you accelerate, ABC knows what’s going on so it increases the pressure in the hydraulic rams at the back to increase the tension in the springs so they don’t compress much. When you brake suddenly, it is the front rams that push the springs up.
Roll reduced by up to 59%
When you corner, the outer hydraulic rams push up on the springs, while the inner ones exert a little less pressure. You can set the suspension to normal or sport mode, to reduce roll, and on average roll is reduced by 17% compared with the previous model with anti-roll bars. On a lane change, the roll angle is halved – down from 6.5 to 3.4 degrees. So you can see that you get a much flatter ride, which reduces the camber and toe-change of the wheels, and makes the car easier to handle.
However, the ride is not completely flat. Because the hydraulic rams increase the compression of the springs, they can only go so far. If they went as far as needed on really hard cornering, they would compress the springs fully, so the car wouldn’t handle at all. So this is a compromise solution, between cost/energy and performance.
But then there’s stability control...
Of course, the stability control works in conjunction with the ABC to give the best cornering power, and is helped by the Senesotronic braking.
… and Sensotronic braking
Now, braking-by-wire seems a bit spooky, but has been thoroughly tested – in fact, to make sure there is always electricity available for it, the SLs have two batteries. The advantages are many. The system can detect an emergency braking situation and act on it from the time it takes you to get your foot from the accelerator to the brake pedal. It can also send signals to the pressurised cylinders at the wheels to wipe the disc with the pads every so often in wet weather.
It can distribute the braking power to the wheels in proportion to how they can use it, rather than acting afterwards with conventional ABS. Also, if you brake during cornering, it puts more braking effort through the outer discs than the inner ones, as this improves cornering power. It is also a more compact system than a normal ABS, but is expensive.
Rack and pinion steering
Just to round things off, there’s rack and pinion steering instead of the recirculating ball system on the previous model, which gives much more feel, and is more precise. It wins all round, and is speed sensitive – you get more assistance at low speeds.
You also get pretty get wheels and tires to handle all that power: 8.5 inch front and 9.5 inch rear rims, with 255/50 front and 285/35 section rear tires.
